Gas seal

ABSTRACT

Disclosed is a gas seal for sealing the upper opening of a large-volume container, the container exhibiting a wall encircling the opening. The gas seal comprises a gas holder foil  1  resting in its peripheral area in the area of the wall, at least four pinch plates  6  mounted circumferentially on the upper edge of the wall, and a sealing cord  4 . The peripheral area of the gas holder foil  1  is overturned and the sealing cord  4  inserted circumferentially in the overturned gas holder foil  1 . The pinch plates  6  squeeze the gas holder foil  1 , in its overturned area, to the upper edge of the wall.

This Application claims priority to German Patent Application DE 20 2005011 689.0, filed Jul. 21, 2005.

FIELD OF THE INVENTION

The present invention relates to a gas seal for the gas-tight sealing oflarge-volume containers by means of a gas holder foil.

BACKGROUND OF THE INVENTION

Biogas plants produce methane through a microbial degradation process oforganic substances. Here, the biogas is created in a multistage processof fermentation or digestion through the activity of anaerobicmicroorganisms, i.e. under exclusion of air. The type of organism strainis determined substantially by the specific process parameters, such astemperature, substrate, pH value, etc. In this way, an adaptation of themicroorganisms to the appropriate substrate is achieved, which makes itpossible to degrade a number of organic materials through fermentation.

The biogas thus created can, in principle, be applied to a number ofutilization options. In the techniques common today, the biogas isusually stored temporarily between creation and utilization, at slightlyelevated pressure in a large-volume container. For practical reasons,storage of the biogas above a fermentation container or liquid manurestorage facility has taken hold. The containers, which usually consistof concrete, but in some cases are also made of other materials, arecommonly spanned with so-called gas holder foils. These foils arerobust, weather resistant and distensible to a certain extent. Gasholder foils usually consist of ethylene propylene diene monomer rubber(EPDM) materials.

Containers spanned with foils in this way are used not only fortemporary storage of biogas, but also for covering liquid manurerepositories and for preventing outgassing of undesired substances fromlarge-volume containers into the environment.

Currently, two fundamentally different technologies are used forfastening the gas holder foil to the container crown.

In the one fastening type, wooden slats having a trapezoidal crosssection are pressed into the wet concrete of the container crown incontainer manufacture. The gas holder foil is squeezed into thetrapezoidal groove encircling the entire container, created when theconcrete sets, by means of said wooden slats of trapezoidal crosssection. Disadvantages of this method lie in the limited weatherresistance of the wood, in the high outlay in manufacturing/mounting thegas seal, and the limited precision in design due to the circumstancesin producing a tall, large-volume container.

The other fastening type uses a fully circumferential metal channelattached to the container crown for fixing the gas holder foil. Here,the foil is squeezed into the channel by means of a tube filled withcompressed air. In addition to the high production outlay, above all thepoor holding power of the metal channel argues against this type of foilfastening. High wind forces are capable of pulling the entire foil outof its anchoring. Moreover, even minimal damage to the tube causes theoutage of the entire fastening. Likewise, in principle, a localizedreplacement of defective sections of the tube is associated with anoutage of the entire fastening.

There is thus a need for a gas seal for large-volume containers having agas holder foil that is easy to mount and, simultaneously, ensures apermanent gas-tight seal of the large-volume container.

SUMMARY

This is where the present invention begins. The object of the presentinvention, as characterized in the claims, is to provide, forlarge-volume containers, a gas seal having a gas holder foil that iseasy and safe to mount, unproblematic to open and multiply resealable,and that simultaneously ensures a gas-tight seal of the large-volumecontainer.

According to the present invention, this object is solved by the gasseal for large-volume containers according to independent claim 1.Further advantageous details, aspects and embodiments of the presentinvention are evident from the dependent claims, the description and thedrawings.

The present invention provides a gas seal for sealing the upper openingof a large-volume container, the container exhibiting a wall encirclingthe opening. The gas seal comprises a gas holder foil resting in itsperipheral area in the area of the wall, at least four pinch platesmounted circumferentially on the upper edge of the wall, and a sealingcord. The peripheral area of the gas holder foil is overturned and thesealing cord inserted circumferentially in the overturned gas holderfoil. The pinch plates squeeze the gas holder foil, in its overturnedarea, to the upper edge of the wall.

In the context of the present invention, the term “large-volumecontainer” is understood to be a container having an internal volume ofat least 10 m³. In particular, the term “large-volume container”includes any type of stationary, immovable container.

According to a preferred embodiment of the present invention, at leastone pinch plate is provided per meter perimeter of the wall of thelarge-volume container. If one pinch plate is mounted per meter of wallperimeter, then a sufficiently tight seal of the large-volume containeris possible.

Particularly preferably, at least two pinch plates are provided permeter perimeter of the wall of the large-volume container. In thisembodiment, the distance between the individual pinch plates is so smallthat a largely complete gas-tight seal of the large-volume container isachieved.

The gas seal according to the present invention can be used for sealingthe gas holder of biogas plants, but it likewise ensures the odor-tightcoverage of liquid manure stores and other large containers outgassingundesirably into the environment. Since, in biogas plants, the fermenteris frequently used as a gas holder, the gas seal according to thepresent invention especially serves to gas-tightly seal fermenters.

For mounting the gas seal according to the present invention, a gasholder foil is laid over the entire container cross section and placedon the upper edge of the wall of the container to be sealed. A sealingcord is laid on the gas holder foil circumferentially on the upper edgeof the wall of the container. The gas holder foil is turned over thesealing cord toward the container interior. Then, in its overturnedarea, the gas holder foil is squeezed inside the sealing cord onto thecontainer crown by means of pinch plates. If the gas holder foil comesunder tension, the sealing cord slips inward until it comes to rest onthe outer edge of the pinch plate and, in this way, safely seals thecontainer.

According to a preferred embodiment of the present invention, the pinchplates are pressed toward the container crown by means of set screws.

According to a further preferred embodiment, each pinch plate issupported on the container crown by one counter bearing per pinch plate,preferably a hinge. If a counter bearing is provided, then high pressurecan be exerted on the gas holder foil also when the pinch plates have alower weight.

Each pinch plate forms, together with a set screw and a counter bearing,a pinch unit.

According to a further preferred embodiment, a squish band isadditionally provided, the pinch plates applying pressure to the squishband and in this way squeezing the gas holder foil in its overturnedarea to the upper edge of the wall of the large-volume container. Byattaching a squish band, a defined smooth surface is created via whichthe pressure exerted by the pinch plates can be transferred to the gasholder foil. In this case, the pinch plates can also exert pressure onthe gas holder foil when the bearing area of the pinch plates is small.This pressure is distributed to a larger area by the squish band,avoiding damage to the foil. A particularly good seal of the containeris achieved with simplified mounting.

According to a further preferred embodiment, additionally, a mountingrail attached circumferentially to the upper edge of the wall of thelarge-volume container is provided, the gas holder foil resting at leastin its overturned area on the mounting rail. By attaching a mountingrail, a defined smooth surface is created on which the gas holder foilrests. If pressure is exerted on the gas holder foil, then, due to thesmooth bearing surface, on one hand, damage to the foil is avoided, andon the other hand, a particularly good seal of the container isachieved.

According to a preferred embodiment of the present invention, themounting rail exhibits a rectangular cross section. Thus, it isespecially a metal band that facilitates the mounting of the gas seal onpre-existing containers. In this way, older containers can beretrofitted with a gas seal. Likewise, pre-existing gas seal systems canbe replaced by a gas seal according to the present invention.

According to a further preferred embodiment of the present invention,the mounting rail exhibits an L-shaped cross section. This embodiment isprovided especially for mounting on containers to be newly erected.Here, one leg of the mounting rail is recessed into the wall of thelarge-volume container.

According to a particularly preferred embodiment, the wall of thelarge-volume container consists of concrete. In this case, after theconcrete is poured into the formwork of the container wall, one leg ofthe mounting rail is pressed into the still wet concrete. After theconcrete has cured, the mounting rail is firmly anchored in the wall ofthe container. For easier mounting, the mounting rail can be furnishedwith additional bearing rails that serve as support on the formwork ofthe container wall.

According to a further particularly preferred embodiment, two pinchunits are provided on each mounting rail. If two pinch units areattached per mounting rail, then, on one hand, the circular crosssection of the container to be sealed can be sufficiently reproduced,and on the other hand, the number of individual units to be mounted iskept as low as possible.

Regardless of the type of foil fastening on the container crown, the gasholder foils currently used cause problems due to the pronouncedtemperature dependence of their distensibility. Under sun exposure insummer, the foil holders expand extremely even when moderately filled.Highly inflated foil containers offer the wind large working surfacesand thus constitute a threat to the entire gas holder. However, the useof tougher EPDM materials is not possible due to the rigidity associatedtherewith at low temperatures.

To solve this problem, according to a further particularly preferredembodiment of the present invention, a net is attached over the gasholder foil. In this way, the distension of the gas holder foil islimited, also under intensive sun exposure, since, when the net iscompletely tautened, no further volume increase of the gas holder foiland thus of the gas holder is possible.

According to a further particularly preferred embodiment of the presentinvention, the net is fastened to the ends of the pinch plates facingaway from the large-volume container. As the gas holder increasinglyfills, via the net, a tension is exerted on the end of the pinch platesfacing away from the container. Via the counter bearings of the pinchplates, this tension is translated into a pressure on the gas holderfoil. In this way, an ever better seal of the container is achieved asthe gas holder becomes increasingly full.

A particularly simple fastening of the net to the ends of the pinchplates facing away from the large-volume container is possible if thepinch plates exhibit eyelets through which the net can be tied to thepinch plates.

The gas seals described in the context of the present invention arepreferably industrially prefabricated. The preferred material for thegas seal components consisting of metal is a corrosion resistant,high-alloy steel. Taken together, the components of the gas seal mountedon the upper edge of the wall of the container to be sealed aretypically between 400 mm and 2500 mm long and between 100 mm and 500 mmwide.

BRIEF DESCRIPTION OF THE DRAWINGS

To illustrate the present invention and to clarify its advantages,exemplary embodiments are specified in the following. These embodimentswill be explained in greater detail in association with the drawings. Itgoes without saying that these details are not intended to limit thepresent invention. Shown are:

FIG. 1 a preferred embodiment of an inventive gas seal in the mountingstate; pictured is a section through the container wall, the sectionplane lying perpendicular to the floor surface of the container;

FIG. 2 a preferred embodiment of an inventive gas seal in the mountingstate, looking down on the upper edge of the wall of the container;

FIG. 3 a preferred embodiment of a gas seal according to the presentinvention; pictured is the section through the container wall accordingto FIG. 1.

MANNER OF EXECUTING THE INVENTION

FIG. 1 shows a gas seal in the mounting state. Pictured is a sectionthrough the container wall, the section plane lying perpendicular to thefloor surface of the container.

The present invention is designed to gas-tightly seal large-volumecontainers by means of foils. It consists substantially of a gas holderfoil 1 and, to be mounted circumferentially on the container crown,units into which the gas holder foil 1 is squeezed. When mounting, thegas holder foil 1 is overturned upwards outside the squish band 3,provided in the resulting crease with a circumferential 15 mm thick EPDMsealing cord and guided back inward under the squish band 3. The squishband 3 is pressed onto the mounting rail 2 by tightening the set screws5 by means of the pinch plates 6. The pinch plate 6 is movably mountedto the hinge 7. In this way, the gas holder foil 1 is squeezed into theunits between the mounting rail 2 and the squish band 3 by means of thepinch plates 6.

The exemplary embodiment describes a gas seal on a circular concretesecondary fermenter having a 9 m radius. The gas holder foil and thesealing cord consist of EPDM. To seal a secondary fermenter having a 9 mradius, a total of 56 individual pinch plates are provided that aremounted circumferentially on the upper edge of the wall of the secondaryfermenter.

In manufacturing the concrete container, the standing formwork 12 isfirst filled with concrete. The individual pinch units are set in thewet concrete. The insertion of the pinch units is facilitated by thesupport rails 10. The support rails are supported on the containerinterior by the formwork 12. On the container exterior, the pinch unitson the mounting rails 2 or the termination brackets 9 mounted thereunderlie on the formwork (see FIG. 2). The mounting rails 2 are designed tobe L-shaped and are provided on the concrete side with attached graspsfor a better metal/concrete connection. Alternatively to the grasps,other details offering form closure can be provided, such as holes inthe rails.

During container construction, the pinch units can be mounted easily,safely and above all precisely on the container crown. After the settingof the concrete and the removal of the formwork, the container can beprovided externally with insulation 14 and trapezoidal sheet metal 15 asshown in FIG. 3. The termination bracket 9 of the units is designed sothat it keeps rainwater off the insulation 14 and can serve to fastenfurther elements, such as notice boards.

On the outside of the pinch plate is located an eyelet for fastening thenet 13. The net 13 lies over the gas holder foil and prevents the gasholder foil from expanding too much when heated or filled too full. If,due to high fullness, the gas holder foil presses against the net, thenthe net, for its part, will pull on the eyelets 8. The tension on theeyelets is diverted by the hinge 7 and causes a stronger squeezing ofthe gas holder foil between the squish band 3 and the mounting rail 2.

If not indicated otherwise, the individual parts of the device accordingto the present invention consist of stainless steel. The mounting rail 2is preferably designed as a bracket in the format 100 mm×10 mm with alength of 990 mm with a steel anchor. The squish band 3 is a flat barwhose cross section measures 35 mm×8 mm and whose length measures 990mm. The set screws 5 are preferably M16 screws having a length of 40 mm.Finally, the pinch plate 6 is likewise preferably a flat bar whose crosssection measures 100 mm×10 mm and whose length measures 150 mm and thatis furnished with fixing pins and an eyelet 8.

1. A gas seal for sealing the upper opening of a large-volume container,the container exhibiting a wall encircling the opening, comprising a gasholder foil (1) resting in its peripheral area in the area of the wall,at least four pinch plates (6) mounted circumferentially on the upperedge of the wall, and a sealing cord (4), the peripheral area of the gasholder foil (1) being overturned, the sealing cord (4) being insertedcircumferentially in the overturned gas holder foil (1), and the pinchplates (6) squeezing the gas holder foil (1) in its overturned area tothe upper edge of the wall.
 2. The gas seal according to claim 1,characterized in that the pinch plates (6) squeeze the gas holder foil(1) in its overturned area to the upper edge of the wall with the aid ofset screws (5).
 3. The gas seal according to claim 1, characterized inthat, additionally, counter bearings (7) are provided, the pinch plates(6) being supported on the upper edge of the wall via the counterbearings (7).
 4. The gas seal according to claim 1, characterized inthat, additionally, a squish band (3) is provided, the pinch plates (6)exerting pressure on the squish band (3) and the gas holder foil (1) inthis way being squeezed in its overturned area to the upper edge of thewall.
 5. The gas seal according to claim 1, characterized in that,additionally, a mounting rail (2) attached circumferentially to theupper edge of the wall is provided, the gas holder foil (1) resting atleast in its overturned area on the mounting rail (2).
 6. The gas sealaccording to claim 5, characterized in that the mounting rail (2)exhibits a rectangular cross section.
 7. The gas seal according to claim5, characterized in that the mounting rail (2) exhibits an L-shapedcross section and one leg of the mounting rail is recessed into thewall.
 8. The gas seal according to claim 7, characterized in that thewall of the large-volume container consists of concrete and one leg ofthe mounting rail (2) is anchored firmly in the concrete.
 9. The gasseal according to claim 1, characterized in that a net (13) is attachedover the gas holder foil (1).
 10. The gas seal according to claim 9,characterized in that the net (13) is fastened to the end of the pinchplates (6) facing away from the large-volume container.
 11. The gas sealaccording to claim 10, characterized in that the end of the pinch plate(6) facing away from the large-volume container is designed as an eyelet(8).
 12. The gas seal according to claim 1, characterized in that atleast one pinch plate (6) is provided per meter perimeter of the wall ofthe large-volume container.
 13. The gas seal according to claim 1,characterized in that at least two pinch plates (6) are provided permeter perimeter of the wall of the large-volume container.